The instant invention resides in the art of validating apparatus and, more particularly, a device which may be used for determining the authenticity of paper money, bank notes, stocks, bonds, and the like. There are presently two known types of such apparatus, designated tray acceptors and slot acceptors, the former receiving the paper money or other security in a tray which is moved to a test position with the security being held stationary during the tests for validity. In such previous known tray acceptors, an optical scanner including a reticle or grid is caused to move across a portion of the security to effect intermittent matching between the reticle and a pattern on the security. Such matching is sensed by an optical sensor which produces an electrical output signal indicative of the validity or invalidity of the paper tendered.
While tray acceptors have been well received in the art, and have provided substantially reliable service, certain disadvantages of such tray acceptors have become apparent. Particularly, the validation test conducted in a tray acceptor generally includes a sensor or reticle which is mechanically moved across the paper a very short distance such that the extent of the test is very limited not only with respect to the actual parameters tested, but also with respect to the fact that only a single area on the paper is being tested. To provide multiple tests in order to defeat photocopies of authentic paper presently known tray acceptors would need to include extremely complex mechanical linkages or a plurality of scanning devices, both alternatives increasing system cost and reducing system reliability.
The instant invention relates to a slot acceptor which, contrary to the previously known tray acceptors, moves the paper past a testing position or positions such that a single sensing system may view plural points on the paper. Slot acceptors can provide multiple tests with only a modest increase in system complexity and are more efficient and reliable in operation since less repair and maintenance is required.
With respect to note acceptors in general, there are a number of typical problems encountered at the hands of those who would seek to either fool the acceptor into believing it has received an authentic paper when, indeed, it has not or who would seek to retrieve the authentic paper after receiving credit from the acceptor for having deposited the paper.
A first problem characteristic of note acceptors is that known as "stringing." In this situation a string or wire is attached to the note when it is deposited in the acceptor and the note is then retrieved via the string or wire after the acceptor has determined the note is authentic and has appropriately credited the depositor with change or goods. It is known that all presently existing acceptors may be "strung." In slot acceptors a valid paper is deposited and the credit issued by the machine is used. The string is used to pull the note back into engagement with the roller used for transporting the paper through the testing path. A second invalid paper is then deposited into the acceptor and when the rollers begin to run in the reverse direction to return the invalid paper the authentic note, previously deposited, is retrieved via the string and roller to the depositor.
Another type of problem which acceptors must overcome is that of determining authentic papers from facsimiles produced by modern photocopy methods. Today, with photocopy machines being capable of producing colored copies of high resolution, sophisticated tests must be provided to guard against the acceptance of a photocopy as a valid paper. The mere utilization of a small duplicity of tests relying on transmission or reflectance of particular spectral wave lengths is no longer sufficient, nor is the utilization of pattern-matching techniques alone.
In the past, persons have also sought to defeat existing note acceptors by use of "mosaics." These mosaics are comprised of small pieces of a valid paper cut from different notes to build a composite which might fool the acceptor. The papers from which the pieces for the mosaic are taken may generally be redeemed from a bank. Often, these mosaics appear to be authentic in the areas to be tested by the acceptor and, since the tested portion of the paper offered to the acceptor is, indeed, authentic, the acceptor will credit the offeror with having deposited a valid paper.
Yet another known approach to defeating existing acceptors is that of "shocking" the machine by physically jarring it in order that a noise signal might be generated. The general approach in this regard is to jar the contacts of a relay closed in order to obtain a vend signal. In slot acceptors where the sensor is fixed and there are a minimum of mechanically moving parts, the susceptibility of the acceptor to "shocking" is minimized.
Other problems inherent in the prior art include the general inability of present validators to obtain a profile of the document offered as a note or other security, relying solely upon one or more individual tests on preselected areas of the document. Such tests do not provide a thorough examination of the paper and are thus susceptible to fraudulent offerings.
Additionally, existing validation apparatus has generally operated in an analog mode, relying upon rudimentary test functions. There are no known acceptors which rely upon a validation transform or equation which is an aggregate of a large number of individual tests wherein the deviation or error of each test is amplified. By operating in a digital mode, a complex validation equation may be used which increases the ability of the validator to discern between valid and invalid papers.